External actuator handle mechanism for enclosed circuit breakers

ABSTRACT

An exterior operating handle is mounted on the wall of the enclosure of an enclosed-type circuit breaker and is drivingly connected to the operating handle of the circuit breaker. The cover is normally latched in closed position by a manually operable latch. Interlock means normally interlock the exterior handle, cover, and enclosure wall in a manner such that (a) when the cover is latched closed, the exterior handle can be operated to open and close the circuit breaker contacts, selectively; (b) when the cover is unlatched and the exterior handle in in ON position, the interlock means becomes operative to prevent opening of the cover; and (c) when the cover is unlatched or open and the exterior handle is in OFF position, the interlock becomes operative to prevent moving the exterior handle to ON position. If the contacts of the circuit breaker become welded together in closed position while the exterior handle is in ON position, and the exterior handle is moved manually to OFF position and the cover is then unlatched, the interlock means, which normally prevent moving the handle to ON position while the cover is unlatched, are defeated for an instant so as to permit the exterior handle to return automatically to ON position, thus preventing a false indication, and then become active again to interlock the cover and enclosure with the exterior handle in ON position.

United States Patent Tadeusz J. Rys Lexington, Ky. 37,521

May 15, 1970 Sept. 28, 1971 Square D Company Park Ridge, Ill.

Inventor Appl. No. Filed Patented Assignee EXTERNAL ACTUATOR HANDLE MECHANISM FOR ENCLOSED CIRCUIT BREAKERS 5 Claims, 6 Drawing Figs.

US. Cl...

Int. Cl Field of Search References Cited UNITED STATES PATENTS 9/1967 Mrenna et a] 200/50 A I-I0lh 9/20 200/50 A ABSTRACT: An exterior operating handle is mounted on the wall of the enclosure of an enclosed-type circuit breaker and is drivingly connected to the operating handle of the circuit breaker. The cover is normally latched in closed position by a manually operable latch.

Interlock means normally interlock the exterior handle, cover, and enclosure wall in a manner such that (a) when the cover is latched closed, the exterior handle can be operated to open and close the circuit breaker contacts, selectively; (b) when the cover is unlatched and the exterior handle in in ON position, the interlock means becomes operative to prevent opening of the cover; and (c) when the cover is unlatched or open and the exterior handle is in OFF position, the interlock becomes operative to prevent moving the exterior handle to ON position.

If the contacts of the circuit breaker become welded together in closed position while the exterior handle is in ON position, and the exterior handle is moved manually to OFF position and the cover is then unlatched, the interlock means, which normally prevent moving the handle to ON position while the cover is unlatched, are defeated for an instant so as to permit the exterior handle to return automatically to ON position, thus preventing a false indication, and then become terior handle in ON position.

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BYJA4442 EXTERNAL ACTUATOR HANDLE MECHANISM FOR ENCLOSED CIRCUIT BREAKERS This invention relates to an operating mechanism for enclosed circuit breakers.

The enclosed type of circuit breaker is mounted in a protective enclosure or box having a hinged cover which can can be latched in the closed position.

The circuit breaker itself may be, for example, one such as disclosed in U.S. letters Pat. No. 3,345,591, of James H. Leonard, issued Oct. 3, I967, and entitled Electric Circuit Breaker with Improved Tripping Means Including a Heater Strip In The Thermal Tripping Means and Adjustable Air Gaps In The Magnetic Tripping Means.

Such a circuit breaker includes a settable operating handle which is rockable, usually upwardly to an ON position and downwardly to an OFF position. Snap-acting lost motion means, including overcenter springs, connect the settable operating handle to the movable contact carrier so that when the settable handle is rocked manually a predetermined distance part way toward either ON and OFF positions, selectively, the movable contacts are moved with a snap action to the final position toward which the handle is being rocked.

The settable operating handle can be rocked a considerable distance in either selected direction before the overcenter springs of the circuit breaker become effective to drive the movable contact carrier. Until the handle reaches the position at which the overcenter springs drive the carrier, it is biased by the spring to return in the direction opposite to that in which it is being moved manually. When the springs do operate, the settable handle is moved to, and yieldably held in, the final position toward which it was being moved manually.

The mechanism for operating the settable handle of the circuit breaker is generally carried on the inside of the sidewall of the enclosure and is provided to provided with an external operating handle.

Various means are employed to latch the cover of the enclosure in closed position, and cover-enclosure-exterior handle interlock means are provided to prevent opening of the cover while the contacts are closed and to prevent closing of the contacts when the cover is unlatched or open.

For example, in the circuit breaker and actuating mechanism disclosed in U.S. Pat. No. 3,272,953, of R. S. Tillson, issued Sept. 13, 1966, a cover-enclosure-external handle interlock is provided wherein a latch for the exterior handle is spring biased so as to latch the exterior handle and thereby prevent rocking it from OFF to ON position when the cover is open. The latch is defeated or rendered inoperative as to its latching operation by means which are rendered effective by closure of the cover.

However, should the circuit breaker contacts in prior structures weld together in ON position it is nevertheless possible to rock the exterior operating handle to OFF position against the force of the overcenter springs of the circuit breaker, which continue to urge the circuit breaker handle back toward ON position.

Thus, with the contacts closed, even if the exterior operating handle is biased to ON position by its return springs, the unlatching of the cover renders the interlock operative so that it latches the exterior operating handle in OFF position despite the fact that the contacts are closed. The inability of the exterior operating handle to return to ON position could result in a false indication.

Attempts have been made unsuccessfully to prevent false indications under such conditions.

In accordance with the present invention, instead of providing overcenter springs in the driving mechanism between the exterior handle and circuit breaker handle, a spring is employed which biases the exterior handle to ON position and moves it toward ON position until it takes and is arrested by an exterior operating handle interlock. The interlock is spring biased to latching position with respect to the exterior operating handle and normally is rendered inoperative when the cover is latched closed, and operative whenever the cover is unlatched or open. This has been necessary to prevent the exterior handle form being returned inadvertently to the ON position to close the contacts when the cover is unlatched. This interlock normally remains effective even when the exterior operating handle is being spring biased toward ON position by the spring of the circuit breaker and its own return spring, which springs, if the contacts are welded in closed position and the exterior operating handle is released, necessarily are biasing the handles and driving mechanism toward the ON position.

In the present invention, the interlock is modified so that the cover in unlatched or partially open, the bias of the springs of the circuit breaker, acting by way of its operating handle, apply force to the interlock mechanism, as the exterior operating handle is biased by its springs toward ON position, and moves the interlock for an instant form its exterior-handlelatching position to that the exterior handle is returned to the ON position by its own biasing spring, or the springs of the circuit-breaker-operating handle. The interlock returns instantly to its cover-interlocking position when the exterior operating handle is moved part way toward ON position.

Thus, when the contacts are welded closed, even though the cover is open or unlatched, the exterior operating handle is returned to the ON position upon its being released by the workman and the cover is thereupon instantly interlocked against opening.

The interlock functions in the usual manner when the cir cuit breaker contacts are unwelded, preventing unlatching and opening of the cover when the contacts are closed, and preventing closing of the contacts by operation of the exterior operating handle when the cover is unlatched or open. Various specific objects and advantages will become apparent from the following description wherein reference is made to the drawings in which:

FIG. 1 is a front elevation of a circuit breaker and enclosure embodying the principles of the present invention, part of the cover being broken away for clearness in illustration;

FIG. 2 is a right side elevation of the structure illustrated in FIG. 1, parts thereof being shown in section for clearness in illustration, and showing the exterior operating handle in ON position with the cover latched;

FIG. 3 is a fragmentary sectional view of the structure illustrated in FIGS. 1 and 2 and taken on the line 3-3 thereof;

FIG. 4 is a fragmentary view of the structure illustrated in FIG. 2, but showing the exterior operating handle in the ex treme position to which it can be moved in the OFF direction;

FIG. 5 is a view similar to FIG. 4 showing the exterior operating handle latched in an OFF position by the interlock; and

FIG. 6 is a view similar to FIG. 2, but showing the position of the exterior operating handle and circuit breaker handle in the position for temporary defeat of the interlock when the circuit breaker contacts are welded closed. Referring to the drawings, a circuit breaker 1 having an operating handle 2 is shown as mounted on the backwall of an enclosure or box 4. The circuit breaker is of the type described in the above patent to James H. Leonard, and the operating handle 2 of the circuit breaker, as therein more fully disclosed, is connected to the movable contact carrier by suitable internal driving mechanism including overcenter springs, not shown. The springs when arranged to snap the movable carrier to ON and OFF positions when the operating handle 2 has been moved a predetermined distance toward the selected one of the positions. These springs necessarily permit a considerable amount of lost motion between the handle 2 in each direction of movement from its normal intermediate position to its selected final operating positions.

The enclosure has a sidewall 5 which is peripherally continuous and provided with a marginal front wall. The open front of the enclosure 4 is closed by a suitable cover 6 having lateral margins 7 terminating in rearwardly extending flanges 8. A suitable sealing annulus 9 is disposed between the margins 7, adjacent the flanges 8, and the inner margin of the front wall.

The operating handle 2 is driven by a driver or operator l2 rotatable on a pivot and having an inwardly extending arm 13 on the inner end of which is mounted a clip or spring yoke 14 between the arms of which the handle 2 is received so that the operator 12 is drivingly connected to the handle 2. In the order to drive the operator 12, an exterior handle 15 is provided alongside the outer face of the sidewall of the enclosure 4.

The handle 15 comprises two spaced arms 151 which lie on opposite sides of a casting 16 which is fixed in relation to the enclosure. The casing 16 has a circumferentially extending slot 160 through which padlock hasps can be passed to lock the exterior handle 15 in selected positions. For driving the circuit breaker handle 2 by the exterior handle 15, the mechanism now to be described is provided.

A suitable drive shaft 17 extends through the sidewall at the latching side of the cover and is mounted for rotation about its axis relative to the sidewall. The outer portion 17a of the shaft 17 is hexagonal. The inner portion of the shaft, indicated at 17a is cylindrical and is mounted in a suitable shaft retainer 18 secured to the sidewall 5 of the enclosure. The handle arms a have hexagonal openings therethrough fitting the hexagonal shaft so that shaft is rotated by and with the exterior handle 15.

Mounted on the hexagonal portion 17a of the shaft 17 within the interior of the enclosure is a cam operator 20 which is rotatable with and by the shaft 17. A cam 21 is mounted on the cylindrical portion 17b of the shaft for rotation relative thereto and is connected to the cam operator 20 for rotation therewith. The cam 21 carries a driving pin 22. The operator 12 is pivotally mounted on the cylindrical portion 17b of the shaft and lies alongside the cam 21. The operator 12 has an internal elongated cam surface 24 which cooperates with the pin 22 for driving the operator 12 with a lost motion relative to the exterior handle 15.

As best illustrated in F168. 4, 5, and 6, the internal cam surface 25 has an internally projecting lobe or peak with a valley 31 at one side of the peak and a valley 32 at the opposite side of the peak. While the exterior handle 15 is in the OFF position, the pin 22 is in the valley 31, and in this position the handle 2 is in OFF position and the circuit breaker is open. Upon rotation of the cam 21 clockwise in FIG. 2, the pin 22 climbs along the left-hand side of the lobe 30, moving the driver 12 clockwise until the handle 2 reaches its dead center position wherein the pin 22 is near the crest of the lobe 30. Thereupon the handle 2 is moved past dead center and drives the contacts of the circuit breaker to closed position with a snap action, and concurrently drives the operator 12 clockwise.

When the pin 22 passes the lobe 30, it will continue to be moved by the cam 21 under the influence of the overcenter springs of the circuit breaker and the return biasing spring which drives the exterior operating handle 15, as is later described.

The axis of the cam 21 is eccentric relative to the axis of the driver, and due to this eccentricity, the pin 22, after passing the lobe, trails behind the right-hand side of the valley 32 and remains spaced therefrom and from the left-hand wall of the valley 32. In this position the operator 12 is free to swing counterclockwise in FIG. 2 until the right-hand wall of the valley 32 engages the pin 22. The counterclockwise movement is sufficient to permit the handle 2 to be moved freely to its intermediate position without hinderance by the cam 21, the exterior handle 15, and the driving connection therebetween, upon tripping of the circuit breaker by an overload.

Upon tripping of the circuit breaker, the exterior operating handle 15 remains in ON position, and it is desirable to indicate the tripped condition of the circuit breaker. For this purpose, a flag 33 is provided and is positioned to be visible through a window 34 on the front cover.

The cam 21 is biased toward an ON position of the circuit breaker by means of a spring 36, one end of which is connected to the cam, as illustrated in FIG. 2, and the other end of which is connected to the shaft retainer l8.

A cover latch, which broadly is of a type disclosed in the prior art, is provided. This latch comprises a sliding strap or bar 40 of metal having at its upper and lower ends fingers 40a, respectively. The latch bar 40 is connected to the cover by suitable rivets 41 extending through elongated slots 42 in the bar 40 so that the bar 40 can be slid endwise to latching and releasing positions. The fingers 4011 have cam surfaces 44, respectively which cooperate with cover hasps 45. Each hasp 45 has an opening 46 therethrough, one edge of which opening provides a cam surface complementary to the associated cam surface 44. Thus, upon moving the latch bar 40 upwardly with the cover closed, the fingers 40a cooperate with the hasps 45 to draw the cover tightly into sealed position on the front of the enclosure, The latch bar 40 carries a suitable arm or projection 47 which cooperates with a spring 48 which biases the latch bar 40 to a released position. The bar 40 is driven to a latched position by means of a sealing lever 50 which is mounted on a sleeve 51 having an external hexagonal periphery fitting a suitable hexagonal opening in the hub of the lever 50. The sleeve 51 has a cylindrical bore 52 which is accommodated on the hexagonal portion 17a of the shaft 17 so that the lever 50 is rotatable relative to the shaft. The hub of the lever 50 is provided with a lug 53 which extends parallel to the axis of the shaft and is received in s suitable slot 54 in the latch bar 40 so as to drive the bar to latching and releasing positions, selectively.

Thus with the bar 40 driven to its latched position, an interlock rocker 57, biased by a spring 58 to locking position, engages a bottom shoulder on the strap 40, as indicated at 59, and prevents unlatching of the strap when the operating handle 15 is in the ON position. The rocker 57 can be defeated by a suitable screwdriver-operating detent 60 which cam be manipulated to release the rocker 57 from its connection with the strap 40 at shoulder 59 regardless of the position of the external operating handle 15.

ln order to prevent the opening of the cover while the breaker is in the ON position, a cover interlock is provided. The cover interlock, indicated at 61, is pivotally mounted on a shaft 62 having at its exterior a suitable slot for receiving a screwdriver for manually defeating the operation of the interlock 61. The interlock 61 has an inwardly projecting portion 63 having spaced arms 63a between which is received the inner end of a cover hasp 64 which is fixedly mounted on the cover. The interlock is biased by a spring 65 to a position effecting engagement of the interlock 61 with the end of a hasp 64 so that the cover cannot be opened when the latch bar 40 is in an unlatching position. It is desirable, however, that the in terlock 61 be such that it is normally held in inoperative position by a suitable lug 66 on the bar 40 when the bar is in latched position. As best illustrated in FIG. 2, as the bar 40 is moved to latched position, it swings the interlock 61 clockwise about the axis of its shaft 62 to an inoperative position with respect to the hasp 64. However, upon movement of the bar 40 to a position which releases the cover for opening, as by the handle 50, the lug 66 is withdrawn from beneath the cover interlock 61 so that the interlock 61 is swung counterclockwise by its spring 65 about the axis of its shaft 62 and into interlocking relation with the inner end of the hasp 64. Thus, the cover is latched against opening by the interlock 61 when the operating handle 15 is in the ON position.

As the exterior operating handle 15 is moved to a position to open the circuit breaker, then the cam 21 is operated to align a reduced-diameter portion 67 with the interlock 61 so that the interlock 61 can be biased by its spring behind a shoulder 68 on the cam 21 in which position the interlock engages the hasp 64. This engagement of the interlock 61 with the shoulder 68 locks the external operating handle 15 against movement to the ON position.

If, under these conditions the contacts are welded in closed position, the external operating handle will be latched in an OFF position when, as a matter of fact, the breaker contacts are closed. Due to this interlock of the shoulder 68 with the interlock 61, the spring 36 is unable to return the operating handle 15 to its ON position to indicate the true condition of the breaker.

In order to prevent such a false indication, the operator 12 is provided with a cam 70 which, as the operator 12 is rotted in a clockwise direction in FIG. 2, by the springs of the circuit breaker when the contacts are welded closed, engages a complementary cam surface 71 on the interlock 61. This biasing force of the springs on the driver 12 bias it toward the closed position, due to the contacts being wheeled and is sufficient to drive the driver 12 bias it toward the closed position, due to the contacts being welded and is sufficient to drive the driver 12 and the operating handle 15 to the ON position when assisted by the spring 36. Since there is a lost motion connection between the operating can 21 and the driver 12, the driver takes over control of the operation and the cam 70 engages the cam surface 71 on the interlock 61, thus releasing the interlock temporarily from the shoulder 68 of the cam. Thus, for an instant the interlock of the handle 15 is defeated by the driver 12 and springs of the circuit breaker sufficiently to allow the shoulder 68 to pass toward the ON position of the handle 15, beyond the complementary shoulder on the interlock.

Accordingly, the exterior operating handle 15 can be moved by its own return spring to the ON position, whereupon the interlock again becomes effective to prevent unlatching of the cover.

As a result of elimination of the overcenter springs of the external operating handle, and as a result of the temporary release of the cover interlock by the operator 12, in event of welding of the contacts closed, the exterior operating handle 15 can always return to ON position as soon as released. Accordingly, the closed condition of the contacts whether due to welding or otherwise, is reflected by the position of the exterior operating handle.

Obviously, when the cover is closed and latched, the interlock 61 is inoperative so that the exterior operating handle 15 can be manipulated to move the operator 12 to circuitbreaker-opening position, and if the contacts are welded closed, the interlock is rendered ineffective so the handle 15 will be returned by its spring 36 back to the ON positions.

Having thus described my invention, I claim:

1. In an enclosure for an enclosed-type circuit breaker, which enclosure has an access opening and a cover therefor;

interlock means normally interlocking the cover and enclosure with the cover in closed position;

an exterior operating handle carried by the enclosure and movable to ON an OFF positions corresponding, respectively, to ON and OFF positions of a circuit breaker to be enclosed;

interlock defeater means driven by the exterior operating handle and operative, when the exterior operating handle is in OFF position, to release the interlock means relative to the cover;

handle latch means connected to the exterior operating handle to latch it in OFF position against return to ON position means biasing the exterior operating handle to ON position;

an operator drivingly connected to the exterior operating handle and adapted to be connected to said enclosed circuit breaker for driving the circuit breaker to ON and OFF positions, selectively, by the exterior operating handle;

characterized in that handle latch defeater means drivingly interconnect the operator and handle latch means for releasing the handle latch means for an instant, when the operator is driven toward ON position other than by the exterior operating handle, thereby to permit return of the handle to ON position, and

means are included to render the interlock defeater means inactive so that the interlock means becomes active relative to the cover, upon return of the exterior operating an openin a Cover for the opening;

a circuit breaker in the enclosure and having an operating handle movable contacts, and springs for opening and closing the movable contacts;

latch means for latching the cover in closed position and for unlatching the cover;

a circuit breaker operator in the enclosure connected to the operating handle for driving the circuit breaker handle to ON and OFF positions, and for being biased by the circuit breaker handle toward ON position of the handle should the circuit breaker contacts be welded together in closed position;

an exterior operating handle mounted on the enclosure and drivingly connected to the operator for driving the circuit breaker, through the operator, to ON and OFF positions, selectively;

interlock means normally operative to interlock the cover against opening when the exterior handle is in ON position and, when the exterior operating handle is in Off position, to release the cover for opening, and to latch the exterior operating handle movement to ON position; characterized in that defeater means drivingly interconnect the interlock, means and operator so that, when the operator is driven toward ON position by the circuit breaker springs due to the contacts being welded closed, and while the exterior operating handle is in OFF position, the defeater means release the exterior operating handle for an instant for return to ON position, and render the interlock means operative to latch the cover against opening, and

means are included to return the operating handle to ON position when it is released by the defeater means.

3. The structure according to claim 2 wherein the interlock means include a cover-enclosure interlock normally operative when said latch means is unlatched and the operating handle is in ON position to latch the cover against opening;

defeater means operated by the latch means to defeat the cover-enclosure interlock when the latch means is latching the cover closed and also when the operating handle is in OFF position;

an exterior handle interlock operative when the cover is unlatched by the latch means and the exterior operating handle is in OFF position, to prevent movement of the exterior operating handle to ON position;

releasing means are provided in the enclosure and are driven by the operator when the operator is moved toward ON position of the circuit breaker by force applied by the circuit breaker while the cover is unlatched, to defeat for an instant the exterior operating handle interlock and permit the exterior handle to return to ON position.

4. The structure according to claim 3 wherein the cover-enclosure interlock and the exterior operating handle interlock are interconnected so that as soon as the exterior operating handle passes the defeated exterior handle interlock while moving toward ON position, the cover-enclosure interlock is rendered operative.

5. The structure according to claim 3 wherein the interlocks comprise a member mounted in the enclosure for rocking about an axis parallel to the rocking axis of the exterior operating handle;

a spring biases the member to a position to latch the cover;

said exterior operating handle has a latch shoulder, said member has a complementary latch shoulder for latching the exterior handle against movement to ON position when the member is moved to cover-releasing position; said member has a defeating cam; and

said operator has a complementary defeating cam operative when the operator is moved to ON position by the circuit breaker, to rock the member to disengage said shoulders, and then permit the member to return to cover-enclosure interlocking position.

22 23 UNTTED STATES PATENT OFFICE CERTIFICATE OF QOERECTION Patent No. b 3, 9, Dated September 28, 1 71 Inventofls) Tadeusz J. Rys

It is certified that error appears in the above'identified patent and that said Letters Patent are hereby corrected as shown below:

Abstract, line 10 change "in" first occurrence) to -is-.

Col. 1, line 6 delete one "can line 35 delete "to provided"; line 70 change "takes" to strickes. Col. 2, line insert "with" after -that; line form" should be from--; line 56 "backwall" should be -back wall 3--; line 62 "when" should be -are--. Col. 3, line 9 "l5 l" should be -l5a-; line ll "casing" should be casting; line "17a" should be -l7b; line 33 "2 should be line 72 "an" should be -the--. Col. L, line 32 "cam" should be can-; line &5 insert "inner before end-. Col. 5, line 2 change "rotted" to --rotated-; lines 6, 7, 8 delete "the driver 12....sufficient to drive";

line +6 "an" should be -and--. Col. 6, line 15 insert "handle after breaker--; line 21 insert "against" after --handle; line insert "operating" after --exterior-.

Signed and sealed this 28th day of March 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Cozmnissioner of Patents 

1. In an enclosure for an enclosed-type circuit breaker, which enclosure has an access opening and a cover therefor; interlock means normally interlocking the cover and enclosure with the cover in closed position; an exterior operating handle carried by the enclosure and movable to ON and OFF positions corresponding, respectively, to ON and OFF positions of a circuit breaker to be enclosed; interlock defeater means driven by the exterior operating handle and operative, when the exterior operating handle is in OFF position, to release the interlock means relative to the cover; handle latch means connected to the exterior operating handle to latch it in OFF position against return to ON position; means biasing the exterior operating handle to ON position; an operator drivingly connected to the exterior operating handle and adapted to be connected to said enclosed circuit breaker for driving the circuit breaker to ON and OFF positions, selectively, by the exterior operating handle; characterized in that handle latch defeater means drivingly interconnect the operator and handle latch means for releasing the handle latch means for an instant, when the operator is driven toward ON position other than by the exterior operating handle, thereby to permit return of the handle to ON position, and means are included to render the interlock defeater means inactive so that the interlock means becomes active relative to the cover, upon return of the exterior operating handle to ON position.
 2. In an enclosed-type circuit breaker: an enclosure having an opening; a cover for the opening; a circuit breaker in the enclosure and having an operating handle movable contacts, and springs for opening and closing the movable contacts; latch means for latching the cover in closed position and for unlatching the cover; a circuit breaker operator in the enclosure connected to the operating handle for driving the circuit breaker handle to ON and OFF positions, and for being biased by the circuit breaker handle toward ON position of the handle should the circuit breaker contacts be welded together in closed position; an exterior operating handle mounted on the enclosure and drivingly connected to the operator for driving the circuit breaker handle, through the operator, to ON and OFF positions, selectively; interlock means normally operative to interlock the cover against opening when the exterior handle is in ON position and, when the exterior operating handle is in OFF position, to release the cover for opening, and to latch the exterior operating handle against movement to ON position; characterized in that defeater means drivingly interconnecT the interlock means and operator so that, when the operator is driven toward ON position by the circuit breaker springs due to the contacts being welded closed, and while the exterior operating handle is in OFF position, the defeater means release the exterior operating handle for an instant for return to ON position, and render the interlock means operative to latch the cover against opening, and means are included to return the operating handle to ON position when it is released by the defeater means.
 3. The structure according to claim 2 wherein the interlock means include a cover-enclosure interlock normally operative when said latch means is unlatched and the operating handle is in ON position to latch the cover against opening; defeater means operated by the latch means to defeat the cover-enclosure interlock when the latch means is latching the cover closed and also when the operating handle is in OFF position; an exterior handle interlock operative when the cover is unlatched by the latch means and the exterior operating handle is in OFF position, to prevent movement of the exterior operating handle to ON position; releasing means are provided in the enclosure and are driven by the operator when the operator is moved toward ON position of the circuit breaker by force applied by the circuit breaker while the cover is unlatched, to defeat for an instant the exterior operating handle interlock and permit the exterior operating handle to return to ON position.
 4. The structure according to claim 3 wherein the cover-enclosure interlock and the exterior operating handle interlock are interconnected so that as soon as the exterior operating handle passes the defeated exterior handle interlock while moving toward ON position, the cover-enclosure interlock is rendered operative.
 5. The structure according to claim 3 wherein the interlocks comprise a member mounted in the enclosure for rocking about an axis parallel to the rocking axis of the exterior operating handle; a spring biases the member to a position to latch the cover; said exterior operating handle has a latch shoulder, said member has a complementary latch shoulder for latching the exterior handle against movement to ON position when the member is moved to cover-releasing position; said member has a defeating cam; and said operator has a complementary defeating cam operative when the operator is moved to ON position by the circuit breaker, to rock the member to disengage said shoulders, and then permit the member to return to cover-enclosure interlocking position. 